Vertebral column implant

ABSTRACT

A vertebral column implant comprises a connecting element, which is insertable in the vertebral bodies of a vertebral column via several bone screws. The screws are each provided with a head part for receiving the connecting element, by means of which a firm connection is achievable between bone screws and connecting element. The connecting element is composed of rigid sections and elastic sections. Here the rigid sections are connectible to the elastic sections via connecting devices. The connecting devices are designed such that the rigid sections and the elastic sections, in each case connected to one another, are aligned substantially coaxially, and their connection is form-fitting.

This application is a Divisional application of U.S. patent applicationSer. No. 11/976,138, filed Oct. 22, 2007, herein incorporated in itsentirety by reference.

This invention relates to a vertebral column implant, comprising aconnecting element and a multiplicity of bone screws, which arescrewable into the vertebral bodies of the vertebral column and whichare each provided with a head part for receiving the connecting element,with which head parts a firm connection is achievable between bone screwand connecting element, and the connecting element is able to be puttogether from rigid sections and elastic sections.

Vertebral column implants are known in the state of the art in diverseways. One hereby distinguishes between two types of systems, namelystabilizing systems consisting of a rigid connecting element, which haveas their goal a stiffening of the respective vertebral column, andelastic systems, with which a supporting stabilization of the vertebralbodies is achieved, a certain flexibility between the individualvertebral bodies being desired and allowed.

Rigid stabilization systems, which are known in a manifold way, have, asalready mentioned, the goal that problematic vertebral bodies receive astiffening, so that an osseous growing together of the affectedvertebral bodies is achieved. In order to achieve an optimalstabilization, adjacent healthy vertebral bodies must also be included,in addition to the problematic vertebral bodies, which can result in thestiffening taking place over too great an area. Moreover it has oftenbeen noted that with the transition from stabilized to no longerstabilized vertebral bodies the load of the vertebral column is toogreat, so that at this transition point there can be damage as a resultof too great a load on the adjacent vertebral bodies.

As has already been mentioned, through the known elastic systems, thevertebrae are stabilized in a supporting way, a certain flexibilitybetween the vertebral bodies being desired and facilitated, however.This system has the drawback, however, that for greatly affectedvertebral bodies, in which a stiffening would be desired, a stiffeningcannot be attained with these elastic systems; an osseous growingtogether of the affected vertebral bodies cannot be achieved.

Known from US 2006/0142758 A1 is a combined system, in which elastic andrigid stabilization regions are used. Used here as the elasticstabilization element is a helical spring-synthetic materialcombination. This elastic stabilization element is connected to thescrews via a pure clamping connection.

The object of the present invention is to create a vertebral columnimplant, with which it is possible to achieve regionally a rigidstabilization of the vertebral column, while in the bordering area thevertebral bodies are supported and stabilized through an elastic system,without a stiffening taking place, and which makes it possible in anoptimal and simple way to connect the rigid and elastic elements.

This object is achieved according to the invention in that the rigidsections are connectible to the elastic sections via connecting devices,and the connecting devices are designed such that the rigid sections andelastic sections connected together in each case are alignedsubstantially coaxially, and the connection is form-fitting.

Created with this design of the invention is a modular system, in whichthe possibility exists of stabilizing adjacent vertebral bodies rigidly,while further adjacent vertebral bodies are elastically supported andstabilized, a limited possibility of movement being allowed. One therebyhas diverse possibilities of stabilizing the vertebral column regionallyin an elastic or rigid way, without the intervention on the patientbecoming more complex. Thus achieved can be, for example, that thetransition phase from rigidly stabilized vertebral bodies to thevertebral bodies no longer to be stabilized can be designed with morecare via an elastically stabilized region in the transition area. Atleast a partial load relief of the affected vertebral bodies can thus beachieved in the area of transition from the rigidly stabilized vertebralbodies to the no longer stabilized vertebral bodies. With this modularvertebral column implant, optimally adapted solutions in each individualcase thus result in which the connections between the rigid sections andthe elastic sections are optimal through form-locking.

Since the connecting devices are designed such that the rigid sectionsand the elastic sections connected together in each case are alignedsubstantially coaxially, great advantages and simplification resultduring insertion of implants assembled from such rigid and elasticsections.

The rigid sections are preferably made of a metal alloy, in particular atitanium alloy, which results in an optimal tolerance in the patientstreated with such implants.

The elastic sections are preferably made of a biocompatible syntheticmaterial, in particular based on polyurethane, whereby the surface canbe provided with encircling ribs and grooves.

A further preferred embodiment of the invention consists in that theconnecting devices are formed by a U-shaped bow made of a rigidmaterial, which connecting devices have at the bottom of the bow andalong the inner side of the legs grooves and ribs corresponding to theribs and grooves of the elastic sections. Through the co-operation ofthe ribs and grooves in the connecting device of the elastic section andof the U-shaped bow a firm, form-fitting connection is obtained. Apressing of the elastic section, which would be necessary with aclamping connection, and which could lead to a viscoelasticity of theelastic section, can thereby be avoided.

Preferably the U-shaped bow with the inserted elastic section islockable with a locking piece which is insertable between the legs ofthe bow and is held via engagement means. A very simple procedure isthereby obtained for insertion and holding of the elastic section in theU-shaped bow, which can have a positive effect on the duration of theoperative intervention.

Another preferred embodiment of the invention consists in that thelocking piece has on the side facing the section ribs and grooves thatcorrespond to the ribs and grooves of the elastic section when thelocking piece is in the inserted state. Thus the locking piece alsocontributes to the form-fitting connection between the elastic sectionand the U-shaped bow in an optimal way.

The connecting devices are preferably attached in each case at an end ofa rigid section or at the head part of a screw. An optimal configurationof these connecting devices results therefrom. The connecting togetherof the different sections can take place in an optimal way.

A connecting element can also be prefabricated, and can be made up of atlest one rigid and at least one elastic section. Preferably therespective connecting device then includes at the rigid section acoaxial bore whose inner walling is provided with projections, in whichbore the elastic element is insertable in the production process throughcasting or injection molding, whereby a form-fitting connection isobtained. The projections here can have different designs.

A further preferred embodiment of the invention consists in that thehead parts of the screws are separate from the screws, and have areceiving region for receiving a screw, which screw with the head partof the screw is attachable via a clamping screw, with which clampingscrew the rigid section is able to be fixed in the head part of thescrew. In this way the screws can first be inserted in the vertebralbodies, and the head part, in which the sections are able to be held,can be subsequently aligned with respect to the screw and the connectingelement.

Preferably the receiving region of the head part of the screw has theshape of a spherical recess for receiving a screw, and the upper portionof the screw is designed as a spherical head. In this way the head partallows itself to be optimally aligned in relation to the screw and to beadapted to the sections to be received therein.

Embodiments of the invention will be explained more closely in thefollowing, by way of example, with reference to the attached drawing.

FIG. 1 shows in a schematic representation (not to scale) a verticalcolumn implant inserted in the vertical column with a connectingelement, which implant is made up of a rigid section and an elasticsection;

FIG. 2 shows in a three-dimensional representation the vertebral columnimplant, as shown in FIG. 1;

FIG. 3 shows in a three-dimensional representation a view of aconnecting device;

FIG. 4 shows in a three-dimensional representation a view of furtherconnecting devices;

FIG. 5 a shows in a three-dimensional representation a connecting devicewhich is installed on the head part for a screw;

FIG. 5 b is a sectional representation of the connecting deviceaccording to FIG. 5 a;

FIG. 6 shows in a three-dimensional representation another configurationof a possibility for a vertebral column implant;

FIG. 7 is a sectional representation of a screw with head part put on, aconnecting device being installed at the head part; and

FIG. 8 shows in a disassembled, three-dimensional representation a screwwith head part and connecting device installed on this head part.

FIGS. 9 to 12 show various possibilities of connecting elastic sectionsand rigid sections when parts of a connecting element, made up ofelastic and rigid sections, are prefabricated.

As can be seen from FIG. 1, first screws 1 are screwed into vertebralbodies 2. These first screws 1 each bear a first head part 3, which headparts are designed for receiving an elastic section 4, which will stillbe described in detail later. The one end region of the elastic section4 is inserted in a connecting device 5, which connecting device 5 isattached to a rigid section 6, as will also be described in detaillater. This rigid section 6 is held in second head parts 7, which areinstalled on second screws 8, which are likewise screwed into thevertebral bodies 2. The elastic section 4 and the rigid section 6 formtogether the connecting element 9, with which a portion of a vertebralcolumn can be stabilized, with the aid of screws 1 and 8.

FIG. 2 shows first screws 1 with first head parts 3 and second screws 8with second head parts 7. The first head parts 3 are each formed by a

U-shaped bow 10 whose inner sides are provided with ribs 11 and grooves12. The elastic section 4 is likewise provided with encircling ribs 13and grooves 14. The elastic section 4 is inserted in each case in theU-shaped bow 10, the ribs 11 and grooves 12 of the U-shaped bow 10engaging in each case in the ribs 13 and grooves 14 of the elasticsection 4 in a form-fitting way. The respective

U-shaped bow 10 is then locked with a locking piece 15, the lockingpieces 15 being likewise provided with ribs 16 and grooves 17 in thearea facing the elastic section 4 and on the sides, so that theselocking pieces 15 also form a form-fitting connection with the elasticsection 4 and the U-shaped bow 10. The locking piece 15 can be held inthe respective U-shaped bow 10 by a locking means 18. Such screws withthe elastic section and the locking pieces are described, for example,in the European patent application EP-A-1 527 742.

The second head parts 7 of the second screws 8 are likewise designedbow-shaped, so that a rigid section 6 can also be inserted in thesesecond head parts 7 of the second screw 8. This rigid section 6 will beheld in a known way via clamping screws 19 in the second head parts 7 ofthe second screws 8.

Attached to the rigid section 6 is the connecting device 5, with whichthe rigid section 6 and the elastic section 4 are able to be connectedtogether.

This rigid section 6 and the elastic section 4 could also be joinedtogether to form a pre-assembled connecting element 9 and in thispre-assembled state be inserted and fixed in the head parts 3 and 7 ofthe screws 1 and 8 already screwed into the vertebral bodies.

Shown in FIG. 3 is the connecting device 5. For this purpose, a U-shapedbow 20 is formed on the end of a rigid section 6. This U-shaped bow isprovided with two legs 21 and 22. Ribs 24 and grooves 25 are made at thebottom 23 of this U-shaped bow 20 and along the inner side of the legs21 and 22. An end region of the elastic section 4 can then be insertedin this U-shaped bow 20. The ribs 24 and grooves 25 of the U-shaped bow20 then engage in the corresponding ribs 13 and grooves 14 of theelastic section 4. A form-fitting connection is thereby obtained. Theelastic section 4 and the rigid section 6 in the connected state arecoaxially aligned.

The U-shaped bow 20 can be locked by means of a locking piece 26. TheU-shaped bow 20 is designed the same way here as the U-shaped bow 10 ofthe first screw 1, as can be seen in FIG. 2; the locking piece 26 thuscorresponds to the locking piece 15 (likewise FIG. 2). The locking piece26 also has ribs and grooves on the region 27 facing the elasticsection. In addition, corresponding ribs and grooves are also providedon the sides 28 and 29 of the locking piece 26. Thus, in the state ofbeing inserted in the U-shaped bow 20, the locking piece 26 is connectedto the U-shaped bow 20 in a form-fitting way via the grooved sides 28and 29. A form fit also occurs in the region 27, and, to be moreprecise, with the elastic section 4. The locking piece 26 is held in theU-shaped bow 20 via engagement means 30.

The rigid section 6 and the U-shaped bow 20 attached thereto are made ofa metal alloy, in particular a titanium alloy. The elastic section ismade up of a biocompatible synthetic material based on polyurethane,whereby it has the desired flexibility. The locking piece 26 is alsomade of the same material, whereby, for engagement in the U-shaped bow20, the regions bearing the engagement 30 are elastically deformable,and the engagement means 30 are able to engage in the correspondingrecesses 31 of the U-shaped bow 20.

FIG. 4 shows a rigid section 6, on whose two end areas one connectingdevice 5 each is attached, as described in reference to FIG. 3. Anelastic section 4 can be inserted in the U-shaped bow 20 in each case,and can be held with the locking piece 26. Thus a connecting element 9,different when compared to the connecting element 9 shown in FIG. 3, canbe obtained. The rigid section 6 is held by second screws 8, while theelastic sections 4 can be held by first screws 1 (FIG. 2). By means ofthis configuration, two vertebral bodies, for example, could be rigidlystabilized via the rigid section 6 and the corresponding second screws8; the adjacent vertebral bodies, in which the first screws 1 areinserted, can be elastically stabilized.

FIGS. 5 a and 5 b show a connecting device 5, which is attached on thesecond head part 7 of a second screw 8. Here, too, the connecting device5 is configured in a way identical to that described with reference toFIG. 3, with the exception that the U-shaped bow 20 is not attached tothe rigid section 6, but instead to the second head part 7 of the secondscrew 8. As has already been mentioned, the rigid section 6 is held inthe second head part 7 of the second screw 8 via the clamping screw 19.The elastic section 4 is held in the U-shaped bow 20 of the connectingdevice 5, this U-shaped bow 20 being once again locked with a lockingpiece 26.

FIG. 6 shows in an application example three second screws 8 with secondhead parts 7. Inserted in the second head parts 7 of the two secondscrews 8 shown below in FIG. 6 is a rigid section 6, which is held inthe second head parts 7 by the corresponding clamping screws 19.Inserted in the second head part 7 of the second screw 8 shown above islikewise a short rigid section 6, which is not visible in this FIG. 6,and which is held by the clamping screw 19. The two rigid sections 6 areprovided on the ends facing each other with a connecting device 5 ineach case, as these are described with reference to FIG. 3. The twosecond screws 8 shown below are rigidly connected to each other via therigid section 6, and would stabilize in a fixed way the correspondingvertebral bodies. The two second screws 8 shown above are connected toeach other via an elastic section 4; the corresponding vertebrae wouldhereby be elastically stabilized.

It would also be conceivable to use such second head parts 7, providedwith connecting devices 5, as are shown and correspondingly described inFIGS. 5 a and 5 b, instead of the two second head parts 7 shown above.

The connecting element seen and shown from the bottom up in FIG. 6,which is made up of a rigid section 6, an elastic section 4, and again arigid section 6, could also be pre-assembled, and be inserted in thispre-assembled state in the second screws already screwed into thevertebral bodies.

The two FIGS. 7 and 8 show a second screw 8 with a second head part 7,to which head part 7 is attached a U-shaped bow 20 of a connectingdevice 5. The screw 8 is separate from the head part 7. The head part 7has a receiving region 32, which has the shape of a spherical recess 33.The second screw 8 is provided with a spherical head 34. The secondscrew 8 can now be inserted in the second head part 7 in such a way thatthe spherical head 34 of the second screw 8 comes to lie in thespherical recess 33 of the second head part. An insert piece 35 is theninserted on the spherical head 34. The rigid section 6 can now beinserted in the second head part 7 of the second screw 8. This rigidsection 6 is then pressed against the insert piece 35 via the clampingscrew 19, which pressing is passed on to the spherical head 34 of thesecond screw 8, and this spherical head 34 is then fixed in thespherical recess 33. Thereby obtained in a second head part movable inrelation to the second screw 8, which in the inserted and fixed state,however, no longer allows any movement mutually. The second head part 7and thus the rigid section 6 can thereby be adjusted and then fixed inrelation to the second screw 8. The elastic section 4 can then beinserted in den U-shaped bow 20, as already described in the preceding,and can be fixed via the locking piece 26.

Parts of a connecting element or a whole connecting element can also bepre-assembled, consisting of rigid sections and elastic sections, whichare then insertable in the bone screws screwed into the vertebralbodies. The rigid sections and the elastic sections are hereby firmlyconnected together, as will still be described in the following.Correspondingly designed portions of a connecting element can beconnected to each other or to elastic and rigid single sections, itbeing possible for connecting devices once again to be provided for thispurpose, as they have been described in the preceding.

FIGS. 9A and 9B show a first possibility for a connecting device usablefor such a prefabricated portion 36 of a connecting element. Thisportion 36 consists of rigid sections 6 and elastic sections 4, whichare connected together via a connecting device 37. For this purpose,formed on the rigid section 6 at the end is a sleeve 38, which isprovided with a coaxial bore 39. The walling 40 is provided withencircling ribs 41 and grooves 42, which are aligned transversely to thebore 39. In the production process for such a portion 36, the elasticsection 4 is brought into a mold through injection molding or pressurecasting, which mold is closed off on both sides with a rigid section.The injected material of the elastic section 4 completely fills the bore39 of the respective rigid section 6. After the solidification of thematerial, by means of the ribs 41, which are made as projections in thewalling 40 of the bore 39, and grooves 42, one has a firm, form-fittingconnection between the respective elastic section 4 and the respectiverigid section. In the example shown here, the elastic section betweenthe rigid sections also has a ribbed surface; this surface could also besmooth, however.

FIGS. 10A and 10B show another embodiment of a connecting device 37 fora prefabricated portion 36. Provided on the rigid section 6 is onceagain a sleeve 38, which is provided with a bore 39. The walling 40 ofthe bore 39 is provided with projections which have the form of teeth43. After the production process, as it is described above, aform-fitting connection is also achieved here between elastic sections 4and rigid sections 6.

FIGS. 11A and 11B likewise show a form-fitting connection betweenelastic sections 4 and rigid sections 5, provided here in the bottom 44of the bore 39 being a bolt 46 formed with a mushroom-shaped swelling45. Here, too, the walling 40 of the bore 39 is provided with ribs 41and grooves 42, it being possible, however, to do without these. Theelastic section 4 can have a surface here too which is ribbed or smooth.

FIGS. 12A and 12B show another form-fitting connection between elasticsections 4 and rigid sections 6, provided on the rim of the sleeve 38being projections which are designed as a collar 47. This collar 47 canextend over the entire circumference, but it can also be provided withinterruptions, as shown here in FIG. 12B.

The rigid sections 6 shown in FIGS. 9 to 12 are provided in each casewith a formed sleeve. It is also conceivable that the respective bore ismade directly into the body of the rigid section, if the requireddimensions allow this.

With this vertebral column implant according to the invention,practically any desired possibilities of combination result, so that aconnecting element can be constructed which can be inserted in thecorresponding bone screws and which makes possible the desiredstabilization in the individual regions of the vertebral column.

1. A vertebral column implant, comprising a connecting element, amultiplicity of bone screws, the bone screws being screwable intovertebral bodies of a vertebral column, each of the screws beingprovided with a head part for receiving the connecting element, with thehead parts providing a firm connection between the bone screws and theconnecting element, the connecting element including rigid sections andelastic sections, and connecting devices connecting the rigid sectionsand the elastic sections together with the rigid sections and theelastic sections being aligned substantially coaxially by a form-fittingconnection.
 2. The vertebral column implant according to claim 1,wherein the rigid sections are made of a metal alloy.
 3. The vertebralcolumn implant according to claim 1, wherein the elastic sections aremade of a biocompatible synthetic material based on polyurethane.
 4. Thevertebral column implant according to claim 3, wherein the surface ofthe elastic sections is provided with encircling ribs and grooves. 5.The vertebral column implant according to claim 1, wherein theconnecting devices are each attached at an end of the rigid sections. 6.The vertebral column implant according to claim 1, wherein theconnecting devices are each attached at the head part of the screws. 7.The vertebral column implant according to claim 1, wherein the headparts of the screws are separate from the screws, and the head partshave a receiving region for receiving the bone screw, the rigid sectionis fixed in the head part of the bone screw by a clamping screw.
 8. Thevertebral column implant according to claim 7, wherein the receivingregion of the head part of the bone screw has a shape of a sphericalrecess for receiving the bone screw, and an upper portion of the bonescrew includes a spherical head.
 9. The vertebral column implantaccording to claim 8, wherein an insert piece is located between thespherical head of the bone screw and the rigid section.
 10. Thevertebral column implant according to claim 9, wherein the rigid sectionis located between the insert piece and the clamping screw.
 11. Avertebral column implant, comprising a connecting element and amultiplicity of bone screws, the multiplicity of bone screws beingscrewable into vertebral bodies of the vertebral column and each of thebone screws being provided with a head part for receiving the connectingelement, the head parts providing a firm connection between themultiplicity of bone screws and the connecting element, the connectingelement including at least one rigid section and at least one elasticsection, both the at least one rigid section and the at least oneelastic section having two ends, respectively, one of the two ends ofthe at least one rigid section being connectable to one of the two endsof the at least one elastic sections via a connecting device, saidconnecting device being formed on the one end of the two ends of the atleast one rigid section, the connecting device locking the one end ofthe at least one rigid section to the one end of the at least oneelastic section in substantially coaxial alignment, the head part havinga recessed receiving region receiving a spherical upper portion of thebone screw.